Browning, polyphenol oxidase activity and headspace gas composition during storage of minimally processed pears using modified atmosphere packaging

Modified atmosphere packaging was used to prevent browning of minimally processed Conference pears, thus extending their shelf-life. Colour changes as well as PPO activity were strongly influenced by the package headspace gas composition, which was determined by the packaging conditions. The initial colour of minimally processed pears was preserved for several weeks under cold storage in plastic pouches of very low O₂ permeability and an initial atmosphere of 100% N₂. A fractional conversion kinetic model fitted the experimental browning data with high accuracy. Colour degradation (ΔE*) of minimally processed pears occurred exponentially (k_ΔE = 0.019-0.077 day^-1) owing to changes in lightness (k_L = 0.021-0.07 day^-1). In contrast, PPO exhibited a linear increase in activity which could be related to the availability of O₂ in the package headspace.© 2002 Society of Chemical Industry